I. Technical Field
The present invention relates to a method for growing pigs and feed used therefor.
II. Description of the Related Art
In the field of swine production, from the birth to shipping, pigs are generally fed with 5 to 6 types of diets depending on the growth stage thereof. During this period, the body weight of the pigs is increased to about 110 kg, and nutritional requirements for increasing the body weight changes in a short period of time. It is basically impossible to follow the rapid change in the nutritional requirements with only the 5 or 6 types of feed. Therefore, diets containing more nutritions than the required levels depending on the growth stage are usually fed in order to prevent subalimentation. Thus, pigs are always fed with hypernutritive feed. Further, depending on the feedings, subalimentation may be caused. In this case, growth is slow, which is undesirable in view of economy. In the conventional methods, in cases where female pigs and castration pigs are raised together, the contents of the feed are usually so selected as to meet the requirements by the female pigs which demand more nutritions than castration pigs. This also contributes to the continued feeding of hypernutritive diets. With such a conventional feeding, not only are the costs of the diets high due to the use of hypernutritive diets, but also the amount of excretion of the excess nutrition components such as nitrogen is large, which adversely affects the environment. Further, much labor is required for changing the diets while continuously measuring the body weights of the pigs, which is a big obstacle to labor-saving for reducing the production cost.
To overcome this problem, a feeding in which pigs can voluntarily choose the diets required for the growth has been proposed (Nam DS et al., Can. J. Anim. Sci., 75:93-98, 1995). However, partly due to the fact that eating behavior of pigs is not clear, this idea is limited only to the research level. Further, the studies which have been made so far include cases where the pigs themselves cannot select the correct nutrients so that their growth was slower than the conventional methods; and cases where the pigs took excess nutrients so that the raising cost was increased, although it was proved that pigs can selectively have the diet with high nutrients and the diet with low nutrients. Thus, the choice feeding is far from the level which can be practically used.